The object of this research is to further our understanding of the operation of the visual cortex by a combined physiological and anatomical approach. Single neurons in cortical areas 17 and 18 of the lightly anesthetized cat will be recorded extracellularyl with bevelled micropipettes to assess their receptive-field properties as determined by flashing bars and moving bars and edges. Intracellular penetration will be attempted to inject horseradish peroxidase for subsequent identification of neural location and morphology. Successful cases will be subjected to a physiological/morphological comparison that will take advantage of the differences in physiology between areas 17 and 18. The expectation is that morphological analysis, down to ultrastructural level if necessary, will provide structural correlates of spatial and temporal receptive field properties, and also of specifically cortical functions such as orientation selectivity, directional selectivity, and hypercomplexity.